Self-powered bar clamp

Abstract

A hand tool or clamp, which locks itself to a work-piece to thereby free the hands of the user, includes a fixed jaw secured to one end of a slide bar and a movable jaw mounted to the slide bar for movement therealong toward and away from the fixed jaw. The movable jaw is normally spring-biased toward the fixed jaw by a flat coil spring supported on the fixed jaw and connected at its free end to the movable jaw. The spring is uncoiled as the jaws are pulled apart to receive a work-piece, and when either jaw is released, rewinds and rapidly advances the movable jaw along the slide bar into clamping engagement with the work-piece. Additional clamping pressure is provided by a screw mechanism associated with the movable jaw which cooperates with the slide bar to advance the movable jaw toward the fixed jaw and increase the clamping pressure between them.

I claim: 
     
       1. A quick-acting bar clamp comprising: an elongate slide bar;   a fixed jaw and first support means for securing said fixed jaw to one end of said slide bar;   a movable jaw and second support means for mounting said movable jaw on said slide bar for movement therealong toward and away from said fixed jaw;   means including extensible tension spring means connected between said first and second support means for normally pulling said movable jaw toward said fixed jaw, wherein the tension of said spring means is sufficient to self-hold said clamp to a work-piece clamped between its jaws irrespective of orientation while allowing said jaws to be pulled apart by hand, whereby upon release of either jaw after having been pulled apart against the tension of said spring means a distance sufficient to receive a work-piece said spring means rapidly advances said movable jaw toward said fixed jaw for clamping the work-piece between them with a pressure corresponding to the tension of said spring means; and   means supported on said second support means for releasably engaging said slide bar and, when engaged, for greatly increasing the clamping pressure between said jaws over that exerted by said tension spring means alone.   
     
     
       2. A quick-acting clamp as defined in claim 1, wherein said tension spring means is a flat coil spring supported on said first support means and having a free end connected to said second support means and wherein said spring means exhibits substantially uniform tension over the range of distances that the jaws may be pulled apart. 
     
     
       3. A quick-acting clamp as defined in claim 2, wherein said slide bar is a hollow tubular bar having a top wall and at least adjacent first and second side walls; and wherein said flat coil spring is mounted on a pin passing through said first support means transversely of said slide bar, and wherein said spring extends through a transverse slot formed in the upper wall of said slide bar and interiorly of said slide bar for connection at a free end to said second support means.   
     
     
       4. A quick-acting bar clamp as defined in claim 1, wherein said drive means, when engaged, tilts said second support means toward said fixed jaw, and wherein said movable jaw is pivotally supported on said second support means for maintaining parallelism between said movable jaw and said fixed jaw for all angles of tilt of said second support means.   
     
     
       5. A quick-acting clamp as defined in claim 1, wherein said first and second support means each has a front portion facing a front portion of the other, wherein a longitudinal axis of each said first and second support means is substantially perpendicular to a longitudinal axis of said slide bar, and wherein said first and second support means each includes means for facilitating hand-grasping the support means and pulling said movable jaw away from said fixed jaw. 
     
     
       6. A quick-acting clamp as defined in claim 5, wherein the front portion of each of said first and second support means has a curved cutout for receiving one or more fingers of a user of the clamp. 
     
     
       7. A quick-acting clamp as defined in claim 2, wherein said free end of said coil spring is connected to said second support means at a point near a front portion thereof for causing said second support means to tilt away from a work-piece clamped between said fixed jaw and said movable jaw, and wherein said drive means, when actuated, tilts said second support means toward a work-piece clamped between said fixed and movable jaws. 
     
     
       8. A quick-acting clamp as defined in claim 7, wherein said drive means comprises a bar extending transversely of a rear portion of said second support means for engaging a top wall of said slide bar when said second support means is tilted away from a clamped work-piece, and means including a screw threadably engaged in said second support means which, when tightened, tilts said second support means and said movable jaw toward said clamped work-piece for increasing the clamping pressure between said fixed and movable jaws over the pressure exerted by said coil spring. 
     
     
       9. A quick-acting bar clamp comprising: an elongate tubular slide bar of rectangular cross-section having a top wall, sidewalls and an elongate slot opposite the top wall;   a fixed jaw having a clamping surface and first support means for securing said fixed jaw to one end of said slide bar with its clamping surface oriented perpendicularly to a longitudinal axis of said slide bar;   a movable jaw having a clamping surface and second support means for mounting said movable jaw on said slide bar for movement therealong toward and away from said first support means, wherein said movable jaw is pivotally supported on said second support means with its clamping surface opposing the clamping surface of said fixed jaw;   means including a partially unwound spring supported on said first means and which extends interiorly of said slide bar and is secured at a free end to said second support means for normally biasing said movable jaw toward and into contact with said fixed jaw, whereby movement of said movable jaw away from said fixed jaw to receive a work-piece therebetween further unwinds said coil spring which, when the movable jaw is released, rewinds and rapidly advances said movable jaw along said slide bar into contact with said work-piece for clamping the work-piece between said movable and fixed jaws with a pressure which corresponds to the tension of said coil spring; and   drive means including a screw threadably engaging said second support means for releasably engaging said slide bar which, when actuated, locks said second support means to said slide bar at a position to which it was advanced by said coil spring and tilts said second support means toward said fixed jaw for increasing the clamping pressure between said fixed and movable jaws over that exerted by said coil spring.   
     
     
       10. A quick-acting clamp as defined in claim 9, wherein the tension of said coil spring is sufficient to self-hold said clamp to a work-piece irrespective of orientation and exhibits substantially uniform tension over the maximum range of movement of said second support means along said slide bar. 
     
     
       11. A self-powered quick-acting clamp comprising: an elongate hollow tubular slide bar having a U-shaped cross-section;   a fixed jaw having a clamping surface secured to one end of said slide bar;   a movable jaw having a clamping surface slidably mounted on said slide bar for movement therealong toward and away from said fixed jaw;   a partially unwound flat coil spring supported at said fixed jaw which extends interiorly of said slide bar and has a free end connected to said movable jaw for normally pulling the clamping surface of said movable jaw toward the clamping surface of said fixed jaw, wherein the tension of said spring is substantially uniform over the maximum range of movement of said movable jaw and sufficient to self-hold said clamp to a work-piece irrespective of orientation while allowing the jaws to be pulled apart by hand, whereby upon release of either jaw after having been pulled apart against the tension of said spring a distance sufficient to receive a work-piece said spring rapidly advances said movable jaw toward said fixed jaw to clamp the work-piece between their respective clamping surfaces with a pressure corresponding only to the tension of said spring; and   means supported on said movable jaw for releasably engaging said slide bar, said means being user-operated following initial clamping of a work-piece by only the tension of said coil spring and, when operated, greatly increases the clamping pressure over that exerted by the tension of said spring along.